Pressure-sensitive adhesive tapes used as closure tapes on disposable diapers require a special combination of properties. One widely used tape uses paper treated with moisture-resistant polymer as a backing. Paper is a surprisingly expensive material, and its cost is increased by the several treatments to which it is subjected in making the tape suitable for diaper closure use. Further, even treated paper retains a moisture-sensitivity which occasionally weakens it sufficiently to cause it to fail when used in a tape closure for a diaper worn by an active baby. Also, paper is comparatively stiff so that the tape does not flex with the diaper and the edge of a paper tape closure may injure a baby's tender skin.
Cloth-backed tapes can be more attractive, flexible, and tear-resistant than paper but cloth is expensive, special treatments are required to prevent the penetration of adhesive through it, and there is a tendency for it to ravel. Various types of nonwoven tape backings, including the so-called "spun-bonded" polymeric backings are less expensive to make and more ravel-resistant than woven cloth, but their thickness, tear-resistance, etc., are not uniform and their open nature makes application of adhesive coating difficult and expensive.
Film-backing pressure-sensitive adhesive tapes, using backings such a polypropylene, have proven to be generally quite effective for diaper closure tapes but greater latitude in the conditions under which they can be used has also been sought. For example, having tightly closed and adhered one side of a diaper, a person applying the diaper may need to pull strongly on the diaper tape projecting from the other side of the diaper to draw the diaper closed and adhere it in place. This pulling effect, if performed in a rapid or jerky manner, can rupture the tape.